1. Field of the Invention
The present invention relates generally to an air controller for an air pump and, more particularly, to an air controller for an air pump capable of regulating the air delivery rate of an air pump which supplies air for bubbling into a glass-sided tank for aquarium fish.
2. Description of the Related Arts
In general families or at places where a lot of people gather, it has been hitherto common to keep aquarium fish in a glass-sided tank to provide effective accessories in the interior of a room or to please the eyes of visitors. A typical tank for keeping such aquarium fish often has at its bottom a bubble generator into which air is fed from a small-sized air pump to generate air bubbles. A conventional type of the air pump is shown by way of example in FIG. 8. In the diagram, reference numeral 1 denotes a yoke firmly secured to a housing 2 for forming an electromagnetic circuit, 3 denotes a core mounted on the yoke 1, and 4 denotes an electromagnetic coil wound around the core 3 and connected to a power cord 5, the yoke 1, the core 3 and the electromagnetic coil 4 constituting an electromagnetic driving mechanism. Reference numeral 6 denotes an arm, and 7 denotes a magnet fitted to the tip of the arm 6 and adapted to be attracted or repelled by the core 3 in response to the electromagnetic on/off action so as to reciprocate between the yoke 1 and the electromagnetic coil 4. The arm 6 is mounted on the housing 2 displaceably in the direction of the reciprocating motion of the magnet 7. A diaphragm 8 is coupled to the arm 6 at substantially the middle part of the arm 6 in the longitudinal direction thereof. The diaphragm 8 is formed from a resilient material such as rubber capable of being contracted or expanded by an external force, namely the diaphragm 8 is actuated by the electromagnetic action of the electromagnetic driving mechanism, to take in air and then discharge the air through an air outlet 9. Thus, the air can be delivered to the tank by connecting a hose to the air outlet 9.
In the conventional air pump, however, the distance between the magnet 7 and the electromagnetic driving mechanism consisting of the yoke 1, the core 3 and the electromagnetic coil 4 is unitarily determined and ordinarily unchangeable, so that the air delivery rate of the air pump is constant. This can result in non-unique and monotonous bubbling state in the tank and may possibly bore the viewers. It may be also conceivable that in order to alter the distance between the magnet and the electromagnetic mechanism that in an arm mounting portion 10, the arm 6 is positioned closer to the sidewall 2a of the housing 2 or further away from the sidewall 2a. However, such measures would result in deformation of the diaphragm 8 due to excessive force applied thereto, and may possibly prevent smooth air intake and discharge from being carried out.